The present technology relates to an charging device that electrifies to a uniform electrical potential a surface of a photoreceptor that is used in an image forming apparatus that performs image formation by an electrophotographic printing method, and to an image forming apparatus that incorporates this electrification device.
In image formation processing by an electrophotographic printing method, sequentially, an electrification process, an exposure process, a development process, and a transfer process are performed to a surface of a photoreceptor.
In the electrification process, the surface of the photoreceptor is electrified to a uniform electrical potential using an electrification device.
One type of electrification device is a non contact type electrification device that does not contact the surface of the photoreceptor. Such a non contact type electrification device electrifies the surface of the photoreceptor by electric discharge from an electrode to which a high voltage electricity is supplied.
In an electrification device that uses a charger line of diameter from some tens of μm to 150 μm, ozone is generated from the charger line during electric discharge due to application of high voltage electrical power, and this contaminates the environment.
Because of this problem, there is an alternative type of electrification device that uses a needle electrode, with which the amount of ozone generated when a high voltage power supply is applied is small. In such a needle electrode, a plurality of needles are arranged along a direction that is orthogonal to a shifting direction of the surface of the photoreceptor, protruding towards the surface of the photoreceptor. During use, dirt and dust in the vicinity of the portion where a high voltage electric field is generated are adsorbed upon the needles of the needle electrode. If this matter is neglected, it becomes impossible to perform adequate electrical discharge from the needle electrode.
Thus, as for example described in Japanese Laid-Open Patent Publication H11-338265, with such a prior art electrification device, a pair of pad members are provided so as to face one another with the needles of the needle electrode sandwiched between them, and so as to be movable along the direction in which the plurality of needles are arranged. By shifting these pad members along the direction in which the plurality of needles are arranged, the pad members are caused to come into contact with the surfaces of the plurality of needles sequentially, so that dirt and dust adhered to the needles is eliminated.
However, the pad members that are provided to such a prior art type electrification device have been made from materials such as felt or the like. Due to this, it is not possible to apply a sufficient elastic force to these pad members, and the ends of the needles of the needle electrode can easily be deformed. Moreover, the fibers of the felt may be cut by contact with the needles, and loose portions thereof can adhere to the surfaces of the needles, thus contaminating the needle electrode. Furthermore, since the pad members contact the sides of the needles that are parallel to the direction in which they are arranged, accordingly it is not possible reliably to clean the entire tip portions of the needles, which are the portions thereof to which dust can most easily adhere due to application of the high voltage electrical field.
The object of the present technology is to provide an electrification device with which, by shifting an elastic member in which the ends of a plurality of needles of a needle electrode are embedded, along the direction in which the needles are arrayed and past the tips of the needles, the entire tip portions of the needles can be cleaned reliably, without deformation of the needles or adherence of fibers taking place; and to provide an image forming apparatus that incorporates such an electrification device.